This audiologic study is the first of its kind to study the hearing and auditory system of normal healthy aging males over such an extended period of time. The age range (19 +) affords broad bases for accumulation of several sets of data which may prove important in isolating the factors related to the progressive hearing loss of various types seen in the otherwise healthy aging populations of most societies. Audiologic assessment in this population includes traditional measures of puretone and speech thresholds, suprathreshold measures of recognition for speech in quiet, in noise at intense levels, as well as studies of dichotic function, time-altered speech stimuli, and other special auditory tests. Electrophysiologic measures of middle ear function, acoustic reflex thresholds and decay, as well as studies of evoked responses are also included. All of these test procedures are repeated with each patient's return to NIH as part of the larger NIA study of normally aging males.